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Chemistry Forums for Students => Analytical Chemistry Forum => Topic started by: kriggy on March 31, 2015, 12:17:51 PM

Title: retention time in HPLC
Post by: kriggy on March 31, 2015, 12:17:51 PM

Hi there, I was doing HPLC analysis of my reaction and question occured to me:
Is it possible that by changing method - specificaly mobile phase gradient - that peak of one compund change its retention time, while the other doesnt?
compound A: RT 1,04 in one gradient and 1,71 in second
compound B: RT 1,33 in one gradient and 1,31 in second

Ive seen that usualy both compound change their retention times but Ive never seen that only one does. I see no reason why this couldnt happen but it seems weird.

Thanks

Title: Re: retention time in HPLC
Post by: Arkcon on March 31, 2015, 12:53:10 PM

Yes, that is possible to have.  You can even cause peaks tow switch positions, just by changing the gradient slope.  If you want to test such a thing out, look for a computer program called Drylab (and there are others) that will let you play with these sorts of experiments, without using up instrument time.

Title: Re: retention time in HPLC
Post by: kriggy on March 31, 2015, 02:23:35 PM

Thanks its not that big of a deal, the MS and UV/VIS match so it is my compound, just the switch of the position of the peaks confused me